The invention relates to a plug-in connector of an electrical device with contact pins which are embedded in a plastic member.
Electrostatic discharges can occur when packaging, handling or connecting electrical devices, for example control devices for motor vehicles. In order to prevent damage to sensitive electronic components by electrostatic discharges, components such as capacitors, coils or varistors which are relatively expensive and require installation space are frequently provided for each contact pin of a plug-in connector.
Published Non-Prosecuted Patent Application DE 43 26 486 A1 discloses a filter plug with a block body which is produced from a mixture of insulating material and ferrite powder for the purpose of suppressing radio-frequency interference.
The application of electrically conductive plastics to avoid electrostatic charging of housings is known from the document xe2x80x9cElektrisch leitende Kunststoffexe2x80x9d [xe2x80x9cElectrically Conducting Plasticsxe2x80x9d], Carl Hanser Publishers, Munich, Vienna, published by H. J. Mair and S. Roth, page 10. Such a housing consists of a mixture of plastic and carbon black, and is intended to have a surface resistance of less than 109 Ohms.
European Patent Application EP 0 649 150 A1 relates to a composite material which has a filler and a matrix embedding the filler. The filler contains predominantly one component with particles having a core/shell structure. The shells of the particles having a core/shell structure are made from insulating material, whereas the cores of these particles consist of electrically conducting or electrically semiconducting material. Under specific preconditions and with a suitable selection of the material of the cores, the electric conductivity of this composite material can change nonlinearly twice under the influence of an electric field. The first nonlinear change effects a voltage limitation, the second a current limitation.
Published Non-Prosecuted Patent Application DE 37 02 780 A1 describes a carrier for a semiconductor component. A varistor protection device protecting against the effects of electromagnetic fields or static charges is integrated into the carrier. The connections of the semiconductor component to be protected are connected to one another by a sandwich structure. The sandwich structure has a first layer made from a varistor material, a first electrode connected to a given potential, a second layer made from varistor material and a second electrode connected to ground.
U.S. Pat. No. 5,616,881 discloses a base for an igniter of an airbag which has two chambers. Provided in the first chamber is an insert with two plug-in pins and a metal oxide varistor for protecting an igniting device against electrostatic discharge.
It is accordingly an object of the invention to provide a plug-in connector for an electrical device which overcomes the above-mentioned disadvantages of the heretofore-known plug-in connectors of this general type and which provides protection against electrostatic discharge and is particularly easy to manufacture in terms of production engineering and requires no additional installation space for the protection against electrostatic discharge.
With the foregoing and other objects in view there is provided, in accordance with the invention, a plug-in connector for an electrical device, having:
a plastic member including a material having conductive properties at voltages above a given working voltage range and having insulating properties at voltages in the given working voltage range; and
contact pins embedded in the plastic member.
In accordance with another feature of the invention, the material is disposed in a form-fitting manner around the contact pins, the plastic member has a conducting surface, and the conducting surface electrically contacts the material and is disposed at a respective spacing distance from the contact pins.
In accordance with yet another feature of the invention, the material is a varistor material.
In accordance with a further feature of the invention, the material is a mixture of a plastic and carbon powder.
In accordance with yet a further feature of the invention, the plastic member includes a base material, and the material is a mixture of the base material and carbon powder.
In accordance with another feature of the invention, the material includes between 5 and 15 percent by weight of carbon powder.
In accordance with yet another feature of the invention, the plastic member includes a crystalline component and a noncrystalline component.
In order to avoid electrostatic discharges which put components at risk, the plastic member of the plug-in connector is provided with a material which has conducting properties at voltages in a range between 20 volts and 700 volts. As a result, a harmful electrostatic discharge or a touch current or contact current can be discharged over at least one contact pin of the plug-in connector and over the material which is conducting at a high voltage, such that an excessively high flow of current via the components at risk is avoided. In this case, the electrostatic charge can flow off from the contact pin via the conducting material onto a conducting surface and/or via other contact pins of the plug-in connector which are connected to a ground potential or frame potential.
The conducting properties of the material should be present at voltages which are only slightly above the working voltage defined for the plug-in connector or the working voltage defined for the contact pins. Here, the term working voltage means the voltage which is applied to the contact pins by signals or a power supply. In the case of a working voltage of 14 volts, the breakdown voltage should be approximately at 25 to 30 volts. The material is preferably configured for a breakdown voltage in the range between 25 to 150 volts.
It is possible to prevent an electrostatic discharge directly at components at risk even under unfavorable spatial conditions, since no additional space is required for components. No additional costs arise for components, assembly, printed circuit board area, layout or other structural outlay.
The plug-in connector according to the invention is particularly suitable for electrical igniters which trigger an airbag or a seatbelt pretensioning device in a motor vehicle.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a plug-in connector of an electrical device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.